Could it possibly have been a life-or-death emergency and she was simply panicking in an effort to quickly inject the insulin?

Good thought, but I don't think so. When your blood sugar is too high, you just have effects like dry mouth and being grouchy, and the bad things that happen are only long term. Unless you get high enough for long enough, then you can go into something called DKA, and in that case you need medical help ASAP-nothing you can inject yourself will fix it.

If it were glucagon, used to treat a low blood sugar, then maybe I could buy it. Low blood sugar can cause you to pass out or have a seizure-so you need to treat it with oral or injected sugar ASAP. And people can do strange things when blood sugar is low. If she were injecting glucagon, I would probably give her a pass.

But just the regular dose of insulin? Not really a reason that you'd have to inject that ASAP, none that I can think of. Unless she thinks there is-and in that case, she has been very poorly educated about diabetes.

There are insulin pens, where you dial the dosage and press a button to inject the insulin. I've seen these used quite discreetly in public, say under the edge of a table in a restaurant. If you didn't know what the person was doing, you'd have no clue. However, if you have to lift or move a garment in such a way as to expose large amounts of skin, it would be best to move to a more private room--bedroom, bathroom, even an unoccupied hallway would work.

If the person is using a syringe, they need a space to put the bottle of insulin and the syringe, in order to fill the syringe. While a public bathroom might not be the best place, the bathroom in a private home would be ideal for both filling the syringe and injecting the insulin.

If you need to expose as much skin as the person in the OP did, you need to move away from the main group. It's not so much about injecting the insulin at that point as it is about grownups not removing clothing in public. I don't care if she was injecting insulin, scratching an itch or showing a tattoo, lifting her shirt that much was uncalled for.

This. I think the person in the lead post is a drama queen who was looking for attention.

I've seen someone inject herself discreetly below a restaurant table while carrying on a conversation with her dinner partner on an unrelated subject; I didn't even notice what injection method she used. In another person's home it would be no big deal to excuse yourself for a minute or two to go to another room for this task. If this woman has been diabetic all her life she already knows that. My guess here is that she was trying to steal attention from the guest of honor.